We veterinarians truly only have a small handful of pharmaceutical medications at our disposal to treat painful conditions in horses. When managing chronic pain, often stemming from the musculoskeletal system, those medications become even more limited, especially if the horse cannot tolerate one or more of those products in the long term.
Lori Bidwell, DVM, DACVAA, is a certified veterinary acupuncturist and owner/veterinarian of the Kentucky-based company East West Equine Sports Medicine. She said that there is a dearth of scientific evidence for many of the commonly prescribed medications and alternative therapies used to manage equine pain.
“Marketing and sponsorship are often the reason horse owners and trainers choose some therapeutic options, often ones that have no research to back their marketing claims,” said Bidwell.
While we might not have all of the answers for the “best” way to manage pain, we do have the freedom to try our hands with what we think are viable options. This does mean, however, that veterinarians need to try new medications and protocols, tailoring the treatments to each individual patient.
“There is no road map when treating pain. Every horse, just like [with] people, responds differently to medications,” relayed Bidwell.
In fact, one can suggest that the only wrong way to treat pain is not to treat it at all.
In this article, various options for managing chronic pain in horses are discussed. Holistic products such as Traumeel, Sarapin, Zeel and arnica might also play a valuable role in this arena and are advocated by Tidwell, but this discussion is limited to currently available pharmaceutical treatment options.
Recognizing Chronic Pain
To best address pain, we must anticipate painful situations and/or recognize when a horse is already in pain. Surprisingly, pain recognition remains challenging for owners and even some veterinarians. Barriers to pain management, according to an article coauthored by Debra Sellon, DVM, PhD, DACVIM, a professor at Washington State University’s College of Veterinary Medicine, include the following:
- lack of knowledge of analgesic drugs;
- inadequate pain assessment skills;
- fear of the adverse effects of drugs;
- inadequate communications between doctors and clients; and
- inaccurate assessment of the degree of pain a patient is likely to be experiencing.
“I think there are a lot of owners who are unable to identify low- or even moderate-level discomfort in their horses,” said Rachel Hector, DVM, MS, DACVAA, assistant professor in the Department of Anesthesiology, Colorado State University Veterinary Teaching Hospital.
She added, “For example, many horses with chronic discomfort exhibit behavior problems. Rather than recognizing their horse is in pain, owners instead believe their horse is being naughty, pushy, dominant or stubborn.”
When indicated, veterinarians need to find ways to help owners identify pain in horses. Using pain scales such as the Horse Grimace Scale (HGS) described by Della Costa in 2014 or exemplary images and online tools might help.
“I’ve always liked the concept of asking owners ‘What can your animal do today compared to one year ago? Can he still trot? Canter? Lay down and get up? Eat certain things?’ If the list is significantly shorter than it was, say, six months ago, maybe there’s a quality-of-life situation that needs to be addressed,” advised Hector.
Nonsteroidal Anti-inflammatory Drugs (NSAIDs) for Chronic Pain
While this class of drugs might seem somewhat basic, NSAIDs remain first-line medications for which equine practitioners should reach when faced with a horse in pain. While many practitioners have their favorites go-tos, many choices are available. Adult horse doses suggested by Bidwell are as follows:
|Phenylbutazone||1 g PO q 12 hr|
|Flunizin meglumine||1 mg/kg PO q 12 hr|
|Meloxicam||0.6 mg/kg PO q 24 hr|
|Carprofen||0.7 mg/kg PO q 24 hr|
|Firocoxib||One 57 mg tablet/1000 lb horse PO q 24 hr|
|Naproxen||8 mg/kg PO q 24 hr|
|Ketoprofen||2 mg/kg IV q 24 hr|
“Bute is still the most widely used NSAID due to cost and ease of use,” said Bidwell. “Ketoprofen is expensive, and although the research has proven that it is a good analgesic with a single dose lasting 24 hours, it is not a go-to for most veterinarians.”
In terms of selection, Bidwell said that price and familiarity are important in decision making for every veterinarian.
“Bute is so popular because it is inexpensive and can be given intravenously or orally as a tablet, paste or powder,” Bidwell explained. “Drugs like acetaminophen and naproxen are less attractive because they need to be given with another NSAIDs/medication in order to be most effective.”
Hector added: “I think price, familiarity and availability all affect what people use. Currently, drug prices are all over the place!”
Bidwell noted: “Importantly, if a horse isn’t responding to one NSAID, find a different NSAID that works for that horse.”
Unfortunately, few head-to-head studies are available to provide clear recommendations regarding NSAID selection. One recent study authored by Banse and Cribb (2017) directly compared meloxicam and phenylbutazone using two different models of pain: a mechanical pain model induced by an adjustable heart bar shoe and an inflammatory pain model induced by intra-articular injection of lipopolysaccharide.
In that study, phenylbutazone was administered at 4.4 mg/kg PO q 12 hr and meloxicam was administered at 0.6 mg/kg PO q 24 hr. Phenylbutazone appeared superior to meloxicam for reducing multiple indicators of pain in the heart bar shoe model. In fact, no significant different in lameness was appreciated between horses treated with meloxicam and placebo in that model. In contrast, meloxicam alleviated lameness to a greater degree in the synovitis pain model compared with phenylbutazone.
“Not all NSAIDs are created equal for every condition and every patient,” said Hector. “If a drug is not effective, I would consider switching to a different drug within this class. It’s an easy thing to do and worth a try to see if you get a better response. The patient at the end of the day dictates what works, regardless of what a study says.”
A comprehensive review on NSAIDs has also just been released and may be a valuable source of information for practitioners: Non-steroidal anti-inflammatory drugs in equine orthopaedics (Jacobs et al. 2022; https://pubmed.ncbi.nlm.nih.gov/35076950/).
Adjuncts and Alternatives to NSAIDs
Some horses are either intolerant to NSAIDs or their pain is not sufficiently managed with NSAIDs alone. Only a handful of other pharmaceutical pain medications that can be used either instead of or in addition to NSAIDs are available for horses with chronic pain.
Acetaminophen: “There is a lot of drama with acetaminophen and liver toxicity, but this is actually a really great drug. It is well absorbed and can be combined with an NSAID,” Hector advised.
The dose is 20 mg/kg PO q 12 hr. The tablets can be soaked in water to dissolve them and mixed with a small amount of corn syrup or molasses mixed with grain or alfalfa pellets.
For practitioners who have concerns, Hector recommended performing routine blood work every few months
to check liver values. But, she said, this practice is indicated even for horses on longterm NSAIDs.
Gabapentin: This mediation, indicated for neuropathic pain rather than nociceptive pain, is unreliable at best according to Hector, but it is still worth a try.
“Gabapentin is very poorly bioavailable, and responses are extremely variable. Plus, finding the correct dose can take weeks to months,” Hector said. Nonetheless, Hector noted, “I think that gabapentin is always worth a try if cost and availability don’t preclude an owner from spending money on something else that has better data behind it. That said, I don’t think there are many disadvantages to trying it if it is cost effective.”
In Hector’s opinion, veterinarians are often conservative with their starting doses.
“Considering gabapentin’s poor bioavailability, I believe we aren’t using high enough doses,” Hector said. “I recommend start at 10 mg/kg PO q 8-12 hr and increase from there depending on the horse’s response. And don’t give up too quickly! Dose titration can take a long time.”
In contrast, Bidwell stops when she reaches 10 mg/kg, saying, “I tend to be more conservative with this medication because I am using it as an adjunct to quiet the nervous system and allow other medications (such as an NSAID) to be more effective. I am cautious with higher doses because of the potential for negative side effects. Gabapentin is effective alone as an analgesic in only 30% of people; I think the same is true with horses. This medication can, however, be useful when combined with anti-inflammatory medications.”
Tramadol: While not necessarily endorsing this medication, Hector said that tramadol might be worth a try
for horses with chronic pain such as laminitis. The primary analgesic effect of tramadol comes from its metabolite, which horses produce variably or break down quickly. As a result, expect a lot of individual variation with this medication. On the plus side, tramadol is not particularly expensive and is easily administered orally at a dose of 2-10 mg/kg q 12 hr.
“Again, tramadol is one of those drugs that I am happy for someone to try, but I wouldn’t necessarily expect a miracle in every case,” said Hector. “But if it is a miracle for one horse, that is excellent!” She added, “That is the thing about managing chronic pain. A drug might not work well (or at all!) in every horse, but if given enough options to try, you may find what works well in one horse. For that one horse, that may result in a huge improvement in quality of life.”
Lidocaine Transdermal Patches: “These are useful for horses with neuropathic pain or chronic pain, such as those coming back from a tendon injury,” said Bidwell. “Even horses that underwent adequate rehab from an injury often still have persistent pain. There is potentially a neuropathic component to the injury, and the lidocaine patches can address this pain. The patches complement treatment with an NSAID.”
According to Bidwell, one should clip the hair before applying the patch directly to the affected area and place a bandage over the patch, if the location allows. The horse will show clinical signs of pain relief within 30 minutes after application, and that should be expected to last about 11 hours (so change the patch q 12 hr).
“The patches work locally at nerve receptors responsible for pain,” explained Bidwell. “There are no systemic effects appreciable with the patches.”
Lidocaine patches are also useful for back pain, septic joints and even temporomandibular pain, Bidwell said.
She added, “The biggest challenge with their use in horses is getting the patches to stick appropriately and stay on. Tissue glue can be applied to the edges when dealing with a septic joint, particularly a stifle.”
Future of Pain Management
“Unfortunately, chronic pain is underdiagnosed and undertreated everywhere,” acknowledged Bidwell.
She added that veterinarians “need to be better at helping owners recognize pain and recognize that older horses have changed needs as compared to younger horses. Good horsemanship (turn-out, appropriate diet, appropriate exercise regimens) becomes more important as horses get older. That, combined with appropriate medications or therapies, can allow horses to live longer with quality of life.”
Even when chronic pain is recognized, adequate treatment in a primary care setting remains challenging.
“There are no new drugs in the very near future, which means that practitioners need to look outside the NSAID box for others, like acetaminophen or topical options, for local disease processes,” Hector said. “It is not easy to treat chronic pain in horses. Veterinarians are becoming interested in some of the new options but seem cautious of things they haven’t ever used. Not relying on just one therapy is key, in my opinion.”